System and Method for Adjusting Selected Operating Parameter of Image Forming Device Based on Selected Environmental Conditions to Control White Vector

Abstract

A system for adjusting a selected operating parameter of an image forming device to control white vector based on selected environmental conditions includes an image forming station having a photoconductive surface with a latent image formed by discharged areas leaving non-discharged areas different from the discharged areas, a sensor mechanism for measuring selected environmental conditions of dry-bulb temperature and relative humidity, a control mechanism for reading the sensor mechanism to adjust the voltage bias of a charging unit by an offset applied to the charging unit based on a wet-bulb temperature value so as to minimize white vector without enabling onset of development of toner background on non-discharged areas, and a memory connected to and accessible by the control mechanism and storing a lookup table of a list of wet-bulb temperature values related to measured dry-bulb temperature and relative humidity values and correlated to a list of voltage bias offsets.

Description

CROSS REFERENCES TO RELATED APPLICATIONS[0001]None.BACKGROUND[0002]1. Field of the Invention[0003]The present invention relates generally to an electrophotographic (EP) image forming device and, more particularly, to a system and method for adjusting a selected operating parameter, namely bias voltage of the charge roll, of the image forming device based on selected environmental conditions, namely, wet-bulb temperature values derived from dry-bulb temperature and relative humidity sensor readings, to control white vector, the difference in surface potential of non-discharged areas of a photoconductive (PC) drum from surface potential of a developer roll, and thereby reduce background toner.[0004]2. Description of the Related Art[0005]The electrophotography (EP) process used in image forming devices, such as laser printers and copiers, utilizes electrical potentials between components to control the transfer and placement of toner. These electrical potentials create attractive and r...

AI Technical Summary

Benefits of technology

[0012]The present invention meets this need by providing an innovation that is directed to a more general or global approach to the resolution of the problem of controlling white vector. This approach dispenses with sensing the current condition of white vector in a developed pattern in comparison to a given desired pattern. Instead, this approach is directed toward adjusting an operating parameter, namely, the bias voltage of the charge roll, based on a wet-bulb temperature value derived from dry-bulb temperature and relative humidity readings from sensors of current environmental conditions, by application of an offset voltage value, correlated to the wet-bulb temperature value, instead of the currently-practiced cold start servo voltage. This offset adjustment will allow for better charge roll voltage optimization and optimal white vector control and thus better print quality, obviating the need to sense and then adjust the current condition of white vector in a developed pattern.

[0014]In another aspect of the present invention, a method for adjusting a selected operating parameter of an image forming device based on selected environmental conditions to control white vector includes biasing a charging unit to a voltage operable to charge a surface of a photoconductive unit, discharging selected areas on the surface of the photoconductive unit to form a latent image thereon leaving non-discharged areas different from the discharged areas, biasing a developer unit to a voltage operative to develop with toner the latent image on the discharged areas of the surface of the photoconductive unit, sensing selected environmental conditions of dry-bulb temperature and relative humidity so as to determine wet-bulb temperature values correlated with said dry-bulb temperature and relative humidity, and adjusting the voltage bias of the charging unit by applying an offset thereto correlated to one of the wet-bulb temperature values so as to minimize white vector without enabling onset of development of toner background on the non-discharged areas of the surface of the photoconductive unit. The method further includes storing a lookup table in memory of a list of wet-bulb temperature values correlated to a list of voltage bias offsets, and accessing the lookup table from memory with a wet-bulb temperature value to determine a correlated value of voltage offset biases to apply to the charging unit.

Problems solved by technology

Very large white vector values are not necessarily the most desirable solution because the density of deposited toner and detail of the resulting image may be adversely affected and could lead to background toner if wrong-sign toner (toner charged positively) is present.

Conversely, as white vector values fall, unwanted background toner may begin to appear.

Determining an optimal white vector that is somewhere between these extremes and that accounts for the aforementioned factors and varying operating conditions is a legitimate problem that is not solved by setting a fixed operating point.

Although a majority of image forming devices, such as laser printers, operates in an air-conditioned office environment, such environment may not necessarily be controlled for humidity.

However, print quality requirements have made servo algorithms not accurate enough for optimizing charge roll bias to minimize background toner in all environments.

While the approach of this patent might represent a step in the right direction toward resolution of this problem, its implementation is not always feasible requiring an innovation that will provide an alternative approach to its resolution.

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